Microsoft has accused arch rival Google that they have deliberately nobbled one of their web sites using a “Panda” update to their search engine.
Google said that recent changes to its search system may have reduced the prominence of some popular websites but it was not “deliberate”.
One of the worst hit by the “Panda” update was Ciao.co.uk, a Microsoft-owned company that had been leading an EU competition case against Google.
Its web visibility fell by 94 percent according to analysis by Searchmetrics.
Google’s head of search evaluation, Scott Huffman, told the BBC that it was “almost absurd” to suggest that the results were rigged.
The company regularly changes the algorithms that determine what users see when they search. Such updates are often done to weed out “content farms” – websites that copy material from other sites in order to get hits.
When the update, known as Panda, was rolled out globally on 11 April, Google published a blog post explaining that it was designed to “reduce rankings for low-quality sites”.
Shopping and price comparison sites such as Ciao.co.uk sometimes suffer when Google algorithms change because they carry comments and reviews replicated elsewhere on the internet.